Scalar Golden Reference - 2022.2 English

The following provides example code for the scalar version of 32 taps filter:

static cint16 eq_coef[32]={{1,2},{3,4},...};

//keep margin data between different executions of graph 
static cint16 delay_line[32];

__attribute__((noinline)) void fir_32tap_scalar(input_stream<cint16> * sig_in,
      output_stream<cint16> * sig_out){
  //For profiling only 
  unsigned cycle_num[2];
  aie::tile tile=aie::tile::current();
  cycle_num[0]=tile.cycles();//cycle counter of the AI Engine tile

  for(int i=0;i<SAMPLES;i++){
    cint64 sum={0,0};//larger data to mimic accumulator
    for(int j=0;j<32;j++){
      //auto integer promotion to prevent overflow
      sum.real+=delay_line[j].real*eq_coef[j].real-delay_line[j].imag*eq_coef[j].imag;
      sum.imag+=delay_line[j].real*eq_coef[j].imag+delay_line[j].imag*eq_coef[j].real;
    }
    sum=sum>>SHIFT;
    //produce one sample per loop iteration
    writeincr(sig_out,{(int16)sum.real,(int16)sum.imag});

    for(int j=0;j<32;j++){
      if(j==31){
        delay_line[j]=readincr(sig_in);
      }else{
        delay_line[j]=delay_line[j+1];
      }
    }
  }
  
  //For profiling only 
  cycle_num[1]=tile.cycles();//cycle counter of the AI Engine tile
  printf("start=%d,end=%d,total=%d\n",cycle_num[0],cycle_num[1],cycle_num[1]-cycle_num[0]);
}
void fir_32tap_scalar_init()
{
  //initialize data
  for (int i=0;i<32;i++){
    int tmp=get_ss(0);
    delay_line[i]=*(cint16*)&tmp;
  }
};